My sense of proportion has been hopelessly corrupted by a lifetime of telling girls that six centimeters is actually six inches, so I’m very excited by the prospect of an app that can tell me the size of something just by taking a photo of it.

That app is called CamRuler, and it works by comparing the size of an unknown object to that of a known object. If you ever put a coin or a small model dinosaur into a photo to help show scale, then you already know how it works.